ENERGY
2 Systems
TDN
Calories
GROSS ENERGY
GROSS ENERGY
Feces
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
Urine & Gas
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
Urine & Gas
METABOLIZABLE ENERGY
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
Urine & Gas
METABOLIZABLE ENERGY
Heat increment
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
Urine & Gas
METABOLIZABLE ENERGY
Heat increment
NET ENERGY
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
Urine & Gas
METABOLIZABLE ENERGY
Heat increment
NET ENERGY
Maintenance Gain Reproduction Milk Production
Gross Energy includes all the energy in a feed.
•It is not all available to the animal
•It is determined by how much heat is liberated upon
combustion.
Digestible Energy is how much energy does not end up
in the feces.
•Therefore it was absorbed.
•It is not all used by the animal, some is lost.
Metabolizable Energy is what is left after accounting for
energy in feces, urine and gasses.
•It is still not all available for the animal to use.
Net Energy
• Is what is left after accounting for losses to
feces, urine & gasses and heat increment.
– Heat increment is energy lost in fermentation
and in metabolic processes.
• Net Energy is available for the animal to
use.
• It is not used with the same efficiency for
all processes.
• Net Energy is always used most efficiently
for maintenance.
• Milk production is almost as efficient as
maintenance.
• Gain (growth and fattening) is less efficient.
• Different uses for energy require different
values be used for the energy content of
feeds for each purpose.
• Maintenance needs must always be met first
• This complicates ration balancing.
GROSS ENERGY
Feces
DIGESTIBLE ENERGY
Urine & Gas
METABOLIZABLE ENERGY
Heat increment
NET ENERGY
Maintenance Gain Reproduction Milk Production
Determining Caloric Energy
• Use Paar Adiabatic
Bomb Calorimeter
Steps in determining calories
•
•
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•
Prepare sample (grind, pellet, place in bomb)
Wire bomb and charge with Oxygen
Place in calorimeter in known amount of H2O
Measure initial temperature
Ignite
Measure final temperature
Calculations
• 1 calorie = energy to raise 1 g H2O 1° C
• 1000 cal = 1 Kcal
– (In humans 1 Calorie = 1 Kcal, animal
nutritionists don’t use Calorie vs calorie)
• Temp rise X g H2O = calories in sample
• Cal in sample X amount of feed = Cal in
feed
– same for feces
• Calculate the total calories (or Kcal) (per
day) eaten and excreted (in feces, urine).
• Calculate DE, ME, Net E (must know the
endogenous contribution in Kcal/Kg and %
– For Kcal/Kg divide the Kcal of interest by Kg
consumed
– For %, divide the Kcal of interest by Kcal of
feed consumed (times 100).
TDN
• Total Digestible Nutrients
– Forget that, I consider it a misnomer
– It is really:
• An ENERGY INDEX on a carbohydrate
equivalent basis
• Calculated from proximate analysis
Calculating TDN
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% CP X Digestibility
=
x
% EE X 2.25 X Digestibility = x
% CF X Digestibility
=x
% NFE X Digestibility
=x
-----SUM = TDN
TDN
Example
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Water
Nitrogen
Ether Extract
Crude Fiber
Ash
NFE
12
2
4
10
2
Example
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•
•
•
•
•
Water
12
Nitrogen 2 (2*6.25) 12.5
Ether Extract
4
Crude Fiber
10
Ash
2
NFE
Example
•
•
•
•
•
•
Water
12
Nitrogen 2 (2*6.25) 12.5
Ether Extract
4
Crude Fiber
10
Ash
2
NFE
59.5
Example
digestibility
•
•
•
•
•
•
Water
12
Nitrogen 2 (2*6.25) 12.5
Ether Extract
4
Crude Fiber
10
Ash
2
NFE
59.5
.80
.75
.40
.80
Example
digestibility
•
•
•
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•
Water
12
Nitrogen 2 (2*6.25) 12.5
.80 = 10
Ether Extract
4 * 2.25 * .75 =6.75
Crude Fiber
10
.40 = 4
Ash
2
NFE
59.5
.80 = 47.6
•
• TOTAL (TDN)
-----------------
68.35